1. Technical Field
The present invention concerns a current detection apparatus and in particular a current detection apparatus for detection of a current flowing in a conductor by detection of the magnetic field surrounding the conductor.
2. Discussion of Related Art
Detection of a current flowing in a conductor can be effected in known manner by means of suitable measuring devices, wherein what is referred to as a shunt is used and the voltage at that shunt resistor as a consequence of the current is used as a measurement of the current, with a known resistance value. Such a current measurement procedure however suffers from the disadvantage that an additional highly accurate resistor must be incorporated into the circuit of the current to be measured, for a suitable level of accuracy, so that the conduction resistance overall is increased. A measuring device connected to that resistor for the detection of the applied voltage is moreover at the potential of the line, the current of which is to be measured, so that it is not possible in that way to implement a potential-free measuring operation. Furthermore contact resistances occur at the contact locations of the shunt, and those contact resistances make it necessary to perform particular measures to avoid falsification of the measurement result.
An improvement in current measurement can be achieved by carrying out contact-less and potential-free measurement by means of sensors which are sensitive to a magnetic field, for example Hall sensors. In accordance with the Hall effect, a current occurs after the application of a voltage in an electric conductor if it is in a magnetic field. The current represents a measurement in respect of the strength of the magnetic field so that it is possible by means of the Hall sensors to measure magnetic fields directly and currents related to the magnetic field indirectly.
DE 102 43 645 A1 discloses a galvanically separated and thus potential-free current measurement procedure, wherein a main conductor is divided into substantially parallel conductor branches and one or more Hall sensors is or are disposed in the proximity of the conductor branches. The Hall sensors are exposed to the magnetic field caused by the currents in the conductor branches and after evaluation of the output signals of the Hall sensors it is possible to determine the current flowing in the conductor branches and thus also in the main conductor. The Hall sensor (magnetic field-sensitive sensor) is thus arranged in the far field outside the conductor branches above or below the parallel conductors.
In addition DE 197 41 417 discloses a current measuring device with Hall sensors, wherein, in a compact arrangement for a plurality of phases of a power supply system the respective, substantially strip-shaped conductors of each phase are bent in a U-shape at a predetermined location and are arranged in that region in a common housing. Hall sensors for each of the phases are arranged on a separate board in such a way that when the board is fitted on to the housing with the conductors of the respective phases the region of the Hall elements is inserted into the region of the U-shaped loop of the respective conductors. The Hall sensors can thus detect the magnetic field surrounding the respective conductor and therewith the current flowing in the respective conductor, after suitable evaluation.
In both cases however there is no guarantee of a simple and precise arrangement in respect of the Hall sensors in the region of the conductors through which current is flowing, so that on the one hand a relatively high level of complication and expenditure has to be involved in regard to arranging the Hall sensors and on the other hand measurement inaccuracies can scarcely be avoided, in particular when dealing with small currents to be measured, due to positional tolerances of the sensors.
Therefore the present invention is based on the problem of designing a current detection apparatus in such a way that at least one magnetic field-sensitive sensor can be easily arranged on a current-carrying conductor in a suitable region of the magnetic field.